Conventionally, there has been a proposed technique in which the direction of the rotation plane of wind turbine blades is controlled to be a direction of receiving wind in a wind turbine generator provided on the sea surface.
For example, Patent Literature 1 below proposes a technique for, in a floating wind turbine generator on the sea surface, detecting a yaw angle of a foundation and a relative angle (yaw angle) between a turbine and a tower, and for controlling a yaw driving device so as to reduce the yaw angle of the foundation.